There is known, as the image forming apparatus using an electrophotographic method, a printer provided with a photosensitive member carrying a developer image thereon and a transfer member for transferring the developer image formed on the photosensitive member onto a sheet.
For example, there is proposed a printer provided with a photosensitive member carrying a toner image thereon and a transfer roller for transferring the toner image formed on a surface of the photosensitive member to a recording sheet.
In this printer, transfer bias is made to increase in accordance with an increase in a resistance value of the transfer roller due to an increase in the number of recorded sheets. This configuration can maintain an electric field between the photosensitive member and the transfer roller, thereby preventing degradation in transfer efficiency.